Cellulose acetoacetate esters used in coating compositions

ABSTRACT

Water soluble or water-dispersible cellulose acetoacetate esters are prepared by contacting a cellulose material with diketene, an alkyl acetoacetate, 2,2,6-trimethyl-4H-1,3-dioxin-4-one or a mixture thereof and a carboxylic anhydride in a solvent system comprising lithium chloride plus a carboxamide. Compositions containing the cellulose acetoacetate esters are useful for coatings applications.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional application under 37 CFR 1.60 of prior applicationSer. No. 08/395,020 filed on Feb. 27, 1995 and allowed on Dec. 13, 1995as U.S. Pat. No. 5,521,304, J. Edgar and Jonathan E. Lawniczak for"CELLULOSE ACETOACETATE ESTERS" which is a divisional of Ser. No.08/135,107 filed on Oct. 12, 1993, now U.S. Pat. No. 5,420,267; which isa CIP of Ser. No. 08/109,205 filed on Aug. 19, 1993, now U.S. Pat. No.5,292,877, which is a File Wrapper Continuation of Ser. No. 07/742,821filed on Aug. 9, 1991, now abandoned.

FIELD OF THE INVENTION

This invention relates to cellulose acetoacetate esters, (C(AA)Es) and amethod for their synthesis.

BACKGROUND OF THE INVENTION

Incorporation of acetoacetate groups into polymers is of interest due tothe unique properties of the acetoacetyl group. Acetoacetylated polymersmay be readily crosslinked using a variety of chemistries and may havelower solution viscosity in some cases than the parent polymers. Theymay have higher affinity for water due to the polarity of theacetoacetyl moiety.

Polymers with affinity for water are also increasingly valuablecommercially. Solventborne coatings are rapidly being replaced bywaterborne coatings and other new technologies due to the environmentalconcerns about organic emissions from the manufacture and application ofsolventborne coatings. In this regard, polymers which require a lowamount of solvent to produce a solution with a workable viscosity arealso desirable.

There is a need in art of waterborne coatings for novel resins whichhave desirable properties in many areas, such as water affinity,convenient crosslinking chemistry, good film properties, and goodcompatibility with other coatings resins.

Water-soluble polymers are also valuable for modifying the rheology ofaqueous solutions for other applications. In the food industry, forexample, they are used as thickeners; in the oilfield industry, theyfind use as suspension aids; and in the pharmaceutical industry, theycan be used as excipients.

Polymers which may be dispersed in water, but are not soluble in water,are exceptionally valuable in the coatings industry. They enableformulation of coatings which have low application viscosity, but at thesame time contain low or no amounts of volatile organic solvents.

Acetoacylated cellulose derivatives are of particular interest forcoatings and other industrial applications.

Cellulose is a readily available, naturally occurring polymer. It hasbeen shown that some cellulose esters are biodegradable. Celluloseesters are widely used in coatings, pharmaceutical, and plasticsapplications, and other cellulose derivatives find wide use in oilfieldand food chemical applications.

While cellulose esters containing only acetoacetyl groups may beprepared by addition of diketene or tert-butyl acetoacetate to asolution of cellulose in amide/LiCl solution (where the amide is either1-methyl-2-pyrrolidinone or N,N-dimethylacetamide), there are no generalmethods for preparing cellulose esters containing acetoacetyl inaddition to an aliphatic or aromatic ester group or groups (celluloseacetoacetate ester, or C(AA)E).

There have been only a few references to cellulose acetoacetate estersin the literature, all dealing with cellulose acetate acetoacetates. InMakromol. Chem, 1953, 10, 261-279, Staudinger and Eicher reported thereaction of cellulose diacetate with diketene in acetic acid, withsodium acetate used as the catalyst. They obtained a product with adegree of substitution ("DS") per anhydroglucose unit ("AGU") of 3.0, asmeasured by elemental analysis.

Synthesis of CA(AA) or any other C(AA)E by reaction of diketene plusanother acylating agent with cellulose itself has not been previouslyknown.

Most of the known cellulose solvents are unsuitable for reactions inwhich cellulose hydroxyls serve as nucleophiles. The solvent systemsrecently introduced by C. L. McCormick (U.S. Pat. No. 4,278,790, 1981)and A. F. Turbak, A. El-Kafrawy, F. W. Snyder, Jr., and A. B. Auerbach(U.S. Pat. No. 4,302,252, 1981) are exceptions in that they do permitcertain such reactions. McCormick and Turbak et al. have taught thatcellulose may be dissolved in solutions of lithium chloride in eitherN,N-dimethylacetamide or 1-methyl-2-pyrrolidinone. McCormick has furthertaught (U.S. Pat. No. 4,278,790; Polymer, 1987, 28, 2317-2323) thatelectrophilic reagents may be added to these cellulose solutions toderivatize cellulose. McCormick has prepared cellulose acetate, methylcellulose, cellulose carbamate, and other derivatives (but not CAA orC(AA)E) in this way.

U.S. Pat. No. 5,008,385 issued to Diamantoglou discloses the making ofparticular cellulose derivatives by homogeneous reaction in a mixture ofdimethylacetamide and/or N-methylpyrrolidinone with LiCl, preferablyafter activation of the cellulose starting material in the absence ofLiCl. Diketene is mentioned in a long list of components supportive ofnumerous combinations.

In U.S. Pat. No. 2,521,897, Caldwell describes the reaction of celluloseesters such as cellulose acetate or cellulose acetate butyrate withdiketene in a solvent using an amine such as pyridine as a catalyst. Thedisadvantages of this include the need to esterify cellulose, hydrolyzethe resulting cellulose triester, isolate and dry the product and thenredissolve and react with diketene. The method also has the disadvantageof the need for use of catalysts in each step, which will be difficultto remove as a catalyst or catalyst salt from a product which has highwater affinity.

In U.S. Pat. No. 2,500,029, Hagemeyer describes a process similar tothat of Caldwell for the preparation of C(AA)Es. The only improvementintroduced by Hagemeyer is that the cellulose ester may be reacted withdiketene in a solvent without a catalyst; the reaction is driventhermally. A catalyst is used in the initial esterification ofcellulose. The process has all of the other disadvantages of theCaldwell process as described above.

In Das Papier, 42, No. 12, pp. 690-694 (1988), Diamantoglou, et al.,teaches esterification of cellulose in solution in DMAC/LiCl or NMP/LiClwith carboxylic anhydrides. He teaches the use of strong acids, amines,and metal acetates as catalysts. In two of the examples shown, nocatalyst was used. In these two examples, he observed poor efficiencywith respect to the carboxylic anhydride (25-40%) and low product DS/AGU(0.25-1.20). There were no attempts at acetoacetylation nor were anyC(AA)Es described.

Clearly, a need exists for a process by which C(AA)Es of the desireddegrees of substitution can be prepared directly from solution in orderto assure homogeneous substitution along the polymer chains and optimumproduct solubility. The process must be economical and amenable toscaleup to industrial production. It is desirable to accomplishcellulose acylation without the need for catalysts, so the solvent andlithium chloride could be easily recycled, without interference fromsalt or catalyst residues. It would also be desirable to obtainmaterials from this process which would be soluble in water, and othermaterials, the organic solutions of which would be dispersible in water.

SUMMARY OF THE INVENTION

This invention relates to a process for making cellulose acetoacetateesters having a total DS/AGU of 0.1 to about 3.0, preferably about 0.1to about 2.9. More preferably, the novel, water-dispersible and/orwater-soluble cellulose acetoacetate esters have a DS/AGU of about 0.1to about 1.0, and even more preferably, about 0.4 to about 0.8.

More particularly the process of the present invention comprises:

a process for preparing a cellulose acetoacetate ester, the processconsisting of contacting in any order the following:

(i) a cellulose material,

(ii) a solubilizing amount of a solvent system comprising lithiumchloride plus a carboxamide selected from the group consisting of1-methyl-2-pyrrolidinone, N,N-dimethylacetamide, or a mixture thereof,

(iii) diketene, an alkyl acetoacetate,2,2,6-trimethyl-4H-1,3-dioxin-4-one, an acetoacetate ester or a mixturethereof, and

(iv) an acylating reagent selected from the group consisting of:

(a) an acid chloride combined with an acid acceptor and

(b) a carboxylic anhydride, wherein said components (i) and (ii) arereacted first and components (iii) and

(iv) are contacted in any order with the product of the contacting ofcomponents (i) and (ii),

under conditions to promote formation of the desired celluloseacetoacetate ester having a DS/AGU of 0.1 to about 3.0.

The present invention is also directed to a water-soluble celluloseacetoacetate ester, preferably having a DS/AGU of 0.1 to 1.0, morepreferably, 0.4 to 0.8.

The present invention is further directed to four types of coatingcompositions comprising the cellulose acetoacetate ester of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The unique ability of certain of the acetoacetylated cellulose esters ofthe invention to be completely solubilized by water makes them useful inlow VOC (volatile organic content) coatings, as well as in otherthickener applications. Low VOC is becoming increasingly desirablebecause of environmental and regulatory considerations.

By the term "water soluble" and derivative terms thereof, it is meantthat upon contacting the cellulose acetoacetate ester with an excess ofwater (a solubilizing amount) at 25° C., and optionally mixing, thecellulose acetoacetate becomes solubilized or dissolved, without theneed for additional cosolvents or dispersing aids, at a level of atleast 10 wt. percent, preferably at least 20 wt. percent.

Mixed cellulose acetoacetate esters have been found to be useful incoatings applications because of the low solution viscosity of suchesters, the dispersibility in water of C(AA)E solutions, and thecross-linking chemistry provided by the acetoacetate functionality.

By the term "water-dispersible" and derivative terms thereof, it ismeant that after dissolving the cellulose acetoacetate in organicsolvent, the resultant solution can form a dispersion when agitated inthe presence of water (in excess).

The ability to disperse certain of these C(AA)Es in aqueous dispersionis extremely valuable to the coatings industry, since it permits lowapplication viscosity combined with low VOC.

The practice of the current invention allows for a wide variety ofcellulose starting materials, temperatures, concentrations, nonsolvents,and reactant ratios. A wide variety of C(AA)E's may be produced,depending on the conditions selected.

The cellulose acetoacetate esters of the invention have the desiredDS/AGU and comprise repeating units of the structure: ##STR1## whereinR¹, R², and R³, are selected separately from the group consisting of:hydrogen, acetoacetyl, and R₄ C═O, wherein R₄ is selected from the groupconsisting of alkyl having from about 1 to about 20 carbon atoms,phenyl, naphthyl, and alkenyl having from about 1 to about 20 carbonatoms.

Examples of alkyl groups having from about 1 to about 20 carbon atomsare methyl, ethyl, propyl, pentyl, nonanyl, dodecanyl, 2-propyl,2-methyl-2-propyl, 2-butyl, succinyl, phthalyl, and maleyl. Morepreferred alkyl groups are methyl, ethyl, propyl, pentyl, 2-propyl,2-methyl-2-propyl, succinyl, phthalyl and maleyl.

Examples of phenyl groups are phenyl, 4-methylphenyl, 4-chlorophenyl.

Examples of naphthyl groups are 1-naphthyl, 2-naphthyl.

Examples of alkenyl groups having from about 1 to about 20 carbon atomsare ethenyl, 2-methylethenyl, 2-phenylethenyl and 1-methylethenyl.

The C(AA)E's of the invention typically have an intrinsic viscosity (IV)as measured in dimethylsulfoxide (DMSO) at a concentration of 0.25 gpolymer/100 ml solvent at 25° C. of about 0.05 to about 3.5, preferablyabout 0.2 to about 1.0. The weight average molecular weight (M_(w)) asmeasured by gel permeation chromatography in 1-methyl-2-pyrrolidinoneusing polystyrene standards is typically about 20,000 to about1,000,000.

The cellulose acetoacetate esters of the process invention have totalDS/AGUs of 0.1 to 3.0, preferably, 0.1 to 2.9. The water-solubleacetoacetate esters of the invention have total DS/AGUs of 0.1 to 1.0,more preferably 0.4 to 0.8.

For the purposes of this invention, total DS/AGU is defined as the sumof the degree of substitution of acetoacetyl and the degree ofsubstitution of other ester groups(s).

A wide variety of sources of cellulose may be used for the practice ofthe invention. It should be particularly noted that the crystalstructure of the cellulose starting material is irrelevant, since itwill be destroyed when the cellulose is dissolved. This permits use oflow molecular weight microcrystalline cellulose. Cellulose sourcesuseful in our invention include hardwoods, softwoods, cotton linters,regenerated cellulose, bacterial and microcrystalline cellulose.

The solvent system useful herein and as taught by McCormick and Turbakmust include lithium chloride plus a carboxamide. The carboxamide may be1-methyl-2-pyrrolidinone, N,N-dimethylacetamide, or a mixture thereof.The ratios of salt or solvent to cellulose can vary within a moderatelywide range.

The acetoacetylating reagent may be either diketene,2,2,6-trimethyl-4H-1,3-dioxin-4-one, or an acetoacetate ester whereinthe alkyl group is straight chain or branched and has 1 to 18 carbonatoms. As taught by J. S. Witzeman (Tet. Lett., 1990, 31, 1401-1404),tert-butyl acetoacetate is an especially suitable alkyl acetoacetate oracetoacetate ester because it generates the reactive intermediate,acetylketene, at a high rate.

The other acylating reagent may be carboxylic anhydride. When acarboxylic anhydride is used, it is unexpected that no added catalyst isrequired in the process of this invention. Other activated acylderivatives, such as acid chlorides, may be used as well. Preferred acidchlorides are acetyl chloride, propionyl chloride, butyryl chloride,hexanoyl chloride, lauroyl chloride, and stearoyl chloride. However, inthe case of acid chlorides, an acid acceptor such as pyridine, sodiumbicarbonate, or sodium acetate must be used in combination with theacylating reagent.

Catalysts are not necessary if the process of the current invention iscarried out in the temperature range of 80°-160° C. as described below.Catalysts may be used to permit use of lower temperatures in theprocess. Such catalysts include (but are not limited to) amines(including pyridine, alkylpyridines, triethylamine, and4-dimethylaminopyridine), mineral acids (including sulfuric acid andhydrochloric acid) and alkali or alkaline earth metal salts (includingsodium acetate, lithium chloride). In the case of the use of carboxylicanhydrides, no catalyst is necessary.

In the synthesis process of the invention, the molar ratio of component(iii):component (iv) is that amount that will result in the desiredDS/AGU under the chosen reaction conditions. The amount of component (i)is typically about 0.1 percent to about 8 percent, preferably about 3percent to about 5 percent, based on the weight of the carboxamide. Theamount of lithium chloride is typically about 100 percent to about 300percent, preferably about 150 percent to about 250 percent, based on theweight of component (i).

Conditions suitable for the formation of C(AA)Es can vary widely. Thetemperature of addition of the acylating reagent (carboxylic anhydride,for example) can be from 0°-200° C., with 25°-120° C. most preferred.The acylating reagent addition time can vary over a wide range,depending on the reaction temperature and the capability for heatremoval. The temperature of addition of the acetoacetylating reagent canvary between 0°-200° C. When diketene is used, reaction will occur at auseful rate throughout this temperature range; 80°-120° C. is preferredbecause reaction is instantaneous in that range. When tBAA or TKD isused, reaction will be very slow below about 60° C. The range 90°-120°C. is preferred for tBAA or TKD, because reaction is fast in thattemperature range.

The yield of C(AA)E in the process of the invention is at least about 80percent, preferably at least about 98 percent, said percentages beingbased on the theoretical maximum yield of C(AA)E.

Nonsolvents to be used in the isolation of the C(AA)E can be any solventin which the reaction solvents and by-products are miscible, but inwhich the C(AA)E is insoluble. Preferred nonsolvents include acetone,methanol, ethanol, 2-propanol, and water or mixtures thereof. Aninsolubilizing amount of nonsolvent is generally at least about 900percent, based on weight of nonsolvent per weight cellulose used. Afterinsolubilizing the C(AA)E with nonsolvent, it is typically desired toperform the additional optional step of separating the C(AA)E from thenonsolvent, e.g., by filtration, drying, decantation, washing, and thelike, to result in substantially pure C(AA)E.

The diketene and carboxylic anhydride should be contacted with theproduct of contacting the cellulose with the solvent system of McCormickor Turbak.

The order of addition of the carboxylic anhyride and diketene (or otheracylating and acetoacetylating agents) can be varied. Either reagent canbe added first, or they can be added simultaneously or as a premixture.One would expect that changing the order of addition would change theposition of substitution. This could be derived from Table I asindicated by the marked variation in the Tg of the products that havebeen made using various orders of addition.

The class of C(AA)E's prepared as taught herein have the desirableproperties of ability to form organic solutions of low viscosity,ability to disperse their solutions in organic solvents in water, andthe rich crosslinking chemistry provided by the acetoacetatefunctionality. Some of the C(AA)E's have the desirable property of beingdissolved or dispersed in water without the need of added organiccosolvents or other dispersing aids. These properties provide materialswhich can be formulated into crosslinkable coatings. Fully formulated,pigmented and catalyzed, water-borne C(AA)E enamels are prepared byfirst adjusting the viscosity of a C(AA)E/water solution or aC(AA)E/solvent solution or a C(AA)E/solvent/water dispersion to aGardner-Holdt viscosity of Z1-Z3 (1000 to 3000 cP) then mechanicallydispersing a pigment, such as rutile titanium dioxide, until the desiredfineness-of-dispersion is obtained.

The coating compositions of this invention include compositions (1)-(4)as hereinafter described.

(1) A coating composition comprising:

(A) about 20 to about 80 percent, based on the weight of the totalcoating composition, of one or more of the cellulose acetoacetate estersof the invention, and

(B) about 20 to about 80 percent, based on the weight of the totalcoating composition, of a coating solvent. Preferred coating solventsinclude glycol ethers, ketones, esters, and the like.

Examples of glycol ethers are ethylene glycol propyl ether, ethyleneglycol butyl ether, and propylene glycol methyl ether. Examples ofuseful ketones are acetone, methyl amyl ketone, and n-heptanone.Examples of useful ester solvents are ethyl acetate and n-butyl acetate.

It is preferred that the composition of (1) contain component (A) at 30to 50 percent and component (B) at 50 to 70 percent, based on the weightof the total coating composition.

(2) A coating composition comprising:

(A) about 25 to 75 percent, based on the weight of the total coatingcomposition, of acetoacetates ester product of coating composition (1),and

(B) about 25 to about 75 percent, based on the total coatingcomposition, of water.

It is preferred that the composition of (2) contain component (A) at 40to 60 percent and component (B) at 60 to 40 percent, based on the weightof the total coating composition.

(3) A coating composition comprising:

(A) about 80 to about 95 percent, based on the weight of the totalcoating composition of the cellulose acetoacetate ester product ofcoating composition (2),

(B) about 1 to about 15 percent, based on the weight of the totalcoating composition, of a crosslinking agent, and

(C) 0 to about 19 percent, based on the weight of the total coatingcomposition, of water.

Preferred crosslinking agents for coating composition (3) aresubstituted melamine and urea resins.

It is preferred that the composition of (3) contain component (A) at 85to 90 percent, component (B) at 4 to 10 percent, and component (C) at 0to 10 percent.

(4) A coating composition comprising:

(A) about 85 to about 99 percent, based on the weight of the totalcoating composition, of the cellulose acetoacetate ester product ofcoating composition (1),

(B) about 1 to about 15 percent, based on the weight of the totalcoating composition, of a crosslinking agent, and

(C) about 0 to about 2 percent, based on the weight of the total coatingcomposition, of a catalyst.

For coating composition (4), it is preferred that component (A) ispresent at 87 to 95 percent, component (B) is present at 2 to 12percent, and component (C) is present at 1 to 10 percent.

Isocyanate-containing resins and trimethylolpropane triacrylate are thepreferred crosslinking agents for composition (4). Theseisocyanate-containing resins include resins based onhexamethoxy-diisocyanate (HMDI) and toluene diisocyanate (TDI).

When trimethylolpropane triacrylate is used, it is preferred that thecatalyst is 1,8-diazabicyclo[5.4.0]-undec-7-ene.

When a polyisocyanate resin is used, it is preferred that the catalystis dibutyltindilaurate.

Crosslinking resins, catalysts, rheological additives, anti-settlingagents, tinting pigments, flexibilizing plasticizers and the like can beadded to the dispersion as needed during a final letdown to applicationviscosity. Of course, final viscosity requirements will vary withapplication and will be about 100 cP for air-atomized spraying to about1000 cP for roller coating operations. Other procedures such asmasterbatch preparation and the use of pre-dispersed pigments would alsobe acceptable.

The coatings test procedures used in the description and examples ofthis invention are as follows:

1. Testing Coated Metal Specimens at 100 Percent RelativeHumidity--Cleveland humidity (ASTM Method D 2247)

2. Gardner-Holdt Bubble Viscosity (ASTM Method D 1545)

3. Film Thickness (General Electric Gage, Type B)

4. Film Hardness (Pencil Method, ASTM Method D3363 or Tukon Method, ASTMMethod D1474)

5. Solvent resistance (methylethyl ketone (MEK) dynamic rub test) (seeASTM Method D 1308)

6. Staining Tests (ASTM Method D 1540)

7. Specular Gloss (ASTM Method D 523)

8. Hegmann Fineness-of-Dispersion (ASTM Method D 1210)

As discussed herein, one class of preferred crosslinking agents containsubstituted melamine and urea resins or residues such ashexamethoxymethylmelamine, hexabutoxymethylmelamine,methoxymethylmethylolmelamine, tetramethoxymethylurea, ortetrapropoxymethylurea. Other useful crosslinking materials are amineterminated polyamides, polyoxyethylenes, polyoxypropylenes and the like.Other useful crosslinking agents are polyisocyanate resins such as HMDI,MDI, and the like. Still another useful crosslinking agent istrimethylolpropane triacrylate (reaction catalyzed by1,8-diazabicyclo[5.4.0]-undec-7-ene). Particularly useful crosslinkingmaterials include an amino resin offered by American Cyanamid, CYMEL373, and a polyamine available from Texaco, JEFFAMINE D400, and apolyisocyanate resin available from Miles, Inc., DESMODUR N-75 (reactioncatalyzed by 0.02% dibutyltindilaurate).

The coating composition of the mixture preferably contains at least 0.1percent crosslinking agent, preferably about 1 percent to about 35percent crosslinking agent, and more preferably about 2 to about 25percent, said percentages being based on the weight of the C(AA)E.

The coating composition optionally contains up to about 70 weightpercent based on the weight of coating binder of one or more additionalcoating additives.

A preferred amount of coating additives is about 1 to about 30 percent.Examples of such coating additives include flow control additives suchas silicones, fluorocarbons, or cellulosics; coalescing solvents such asdiethylene glycol monobutyl ether, trimethylpentanediol monoisobutyrate,or ethylene glycol monooctyl ether; strong acid catalysts such asp-toluenesulfonic acid, trichloroacetic acid, ortrifluoromethanesulfonic acid; pigments such as titanium dioxide,barytes, clay, or calcium carbonate; colorants such as phthalocyanineblue, molybdate orange, or carbon black; biocides such as tin compounds(e.g., tributyltin oxide), quaternary ammonium compounds, or iodinecompounds; thickeners such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, ethyl hydroxyethyl cellulose, guar gum and the like.

The Gardner-Holdt viscosity of the coating composition is preferablyabout T to about Z3; more preferably about W to about Z1. Theseviscosity values permit application by spraying and/or wire-roddrawdowns (which simulate a roller coating operation) as practiced inExamples 6-9 hereof.

The coating composition can be prepared by the techniques describedherein and/or by techniques known in the art, e.g., as disclosed in U.S.Pat. Nos. 4,698,391, 4,737,551, and 3,345,313, the disclosures of whichare incorporated herein by reference in their entirety.

The coating composition can be applied onto a substrate and crosslinkedusing techniques known in the art; e.g., by spray-applying 3 to 4 milsof wet coating and baking in a 150° C. forced air oven for 30 minutes,by similarly preparing and baking at a lower temperature of 60° C. forone hour, or in some cases by curing at ambient temperature for 2 to 24hours.

The substrate can be any common substrate such as paper, polymer filmssuch as polyethylene or polypropylene, metals such as aluminum, steel,galvanized steel, glass, urethane elastomers, primed (painted)substrates, and the like.

After the coating composition is coated onto a substrate and cured(i.e., crosslinked) such a cured coating has many desirable propertiessuch as good pencil hardness, good gloss, and good MEK double rubsolvent resistance, and water rub resistance.

Preferred pencil hardness (mar/cut) is about B to about 4H; morepreferred is at least F; preferred gloss at 60° is about 40 percent toabout 100 percent, more preferred is above 60 percent; preferred solventrub resistance is at least about 200, for cured coatings and about 25for thermoplastic coatings. Preferred water rub resistance is about 100.

As appreciated in the art, the exact components and properties ofcomponents desired for any given coating application can vary, andtherefore, routine experimentation may be required to determine theoptional components and proportions of components for a givenapplication and desired properties.

This invention can be further illustrated by the following examples ofpreferred embodiments thereof, although it will be understood that theseexamples are included merely for purposes of illustration and are notintended to limit the scope of the invention unless otherwisespecifically indicated. The starting materials are commerciallyavailable unless otherwise noted. All percentages are by weight unlessotherwise indicated.

EXAMPLES

In the following examples, the cellulose (8 g) and DMAC solvent (300 mL)were added to a 500 mL three-neck round bottom flask equipped withmechanical stirrer, thermometer, nitrogen inlet, and distillation head.The slurry was heated to 100°-140° C. under nitrogen, with stirring.Lithium chloride (15 g) was added all at once, then the slurry washeated to distill off some portion (typically 75-85 mL) of the solvent;this was used as an economical and practical method for removing waterfrom the reaction mixture. This is particularly important since waterwill react unprofitably with the carboxylic anhydrides and diketene, andsince the cellulose, carboxamide solvent, and lithium chloride all arequite hygroscopic. The slurry was cooled to a temperature between10°-150° C., and stirred until the cellulose dissolved. Typically thistook 1-3 hours. The solution was heated to the reaction temperature(110° C. in each of these examples), then the appropriate carboxylicanhydride was added over the specific time (Addition Time A). Thesolution was stirred at the reaction temperature for a specified holdtime (Hold Time A). The specified amount of diketene then was added overa specified time (Addition Time D). The solution was stirred at thereaction temperature for a specified hold time (Hold Time D). Thesolution then was cooled to 20°-40° C. The product was isolated byadding the reaction mixture dropwise to the specified nonsolvent withstrong agitation. The product was washed with the specified amount ofthe specified nonsolvent(s), the specified number of times. The productwas dried in a vacuum oven under nitrogen at 40°-60° C. The yieldsquoted in the examples are of isolated, well-characterized products.DS/AGU (degree of substitution per anhydroglucose unit) was determinedby ¹ H NMR in d-6 DMSO (dimethylsulfoxide) containing several drops oftrifluoroacetic acid (to shift any hydroxyl protons downfield). Gelpermeation chromatography used NMP (1-methyl-2-pyrrolidinone) as solvent(polystyrene reference). Intrinsic viscosity was measured in DMSO(dimethylsulfoxide) solution. Differential scanning calorimetry (20°C./min, second scan, after heating to 225° C. at 20° C./min, and coolingto below 0° C.) was employed to determine Tg's. Representative membersof each family of materials were examined by infrared spectroscopy toconfirm product identity. All temperatures in degrees centigrade.

The low solution viscosities of C(AA)Es are illustrated in Table II.

Table III lists some performance properties of films made from aqueousdispersions of C(AA)Es, both uncrosslinked and crosslinked with melaminecrosslinker.

Table IV lists some performance properties of films made from solutionsof C(AA)Es and from solutions crosslinked with amine (enamineformation), with trimethylolpropane triacrylate (Michael reaction), andwith isocyanate-containing resin.

The data in Tables II-IV illustrate the usefulness of C(AA)Es inproviding high solids solutions which can be dispersed in water andprovide coatings films with varied crosslinking possibilities.

EXAMPLE 1

Reagents set forth below were subjected to the standard proceduredescribed above under the standard reaction conditions, except asdescribed below. The results, in terms of identity and yield of thedesired cellulose acetoacetate ester, and key analyses of the product,are also set forth below.

    ______________________________________                                        Cellulose       Natchez HVX                                                                   (hardwood cellulose                                                           pulp, available from                                                          International Paper in                                                        Natchez, Mississippi)                                         Carboxylic Anhydride                                                                          Acetic Anhydride                                              Equiv           0.3                                                           Addition Time A 3 min                                                         Hold Time A     20 min                                                        Equiv Diketene  1.5                                                           Addition Time D 25 min                                                        Hold Time D     33 min                                                        Nonsolvent      Methanol                                                      Washing         2 × 1L methanol; then                                                   Soxhlet extraction with                                                       methanol                                                      CA(AA) Yield    95% of theory                                                 Key Analyses    DS(acetyl) = 0.12, DS                                                         (acetoacetyl) = 1.29, IV =                                                    2.10, GPC M.sub.n = 66,000, Tg =                                              163, soluble in DMSO and                                                      NMP.                                                          ______________________________________                                    

This example demonstrates synthesis of a cellulose acetate acetoacetateby this process directly from cellulose.

EXAMPLE 2

Reagents set forth below were subjected to the standard proceduredescribed above under the standard reaction conditions, except asdescribed below. The results, in terms of identity and yield of thedesired cellulose acetoacetate ester, and key analyses of the product,are also set forth below.

    ______________________________________                                        Cellulose       Microcrystalline cellulose                                    Carboxylic Anhydride                                                                          Propionic Anhydride                                           Equiv           0.4                                                           Addition Time A 5 min                                                         Hold Time A     16 min                                                        Equiv Diketene  0.2                                                           Addition Time D 2 min                                                         Hold Time D     30 min                                                        Nonsolvent      Methanol                                                      Washing         2 × 1L methanol, then                                                   Soxhlet extraction with                                                       methanol                                                      C(AA)P Yield    87% of theory                                                 Key Analyses    DS(propionyl) = 0.28, DS                                                      (acetoacetyl) = 0.20, IV =                                                    1.13, GPC M.sub.n = 47,000, Tg =                                              213, soluble in water,                                                        DMSO and NMP.                                                 ______________________________________                                    

This example demonstrates synthesis of a water-soluble celluloseacetoacetate propionate by this process, and also demonstrates that eventhe highly crystalline microcrystalline cellulose is a suitable startingmaterial for this process.

EXAMPLE 3

Reagents set forth below were subjected to the standard proceduredescribed above under the standard reaction conditions, except asdescribed below. The results, in terms of identity and yield of thedesired cellulose acetoacetate ester, and key analyses of the product,are also set forth below.

    ______________________________________                                        Cellulose       Microcrystalline cellulose                                    Carboxylic Anhydride                                                                          Butyric Anhydride                                             Equiv           0.3                                                           Addition Time A 10 min                                                        Hold Time A     21 min                                                        Equiv Diketene  0.3                                                           Addition Time D 3 min                                                         Hold Time D     32 min                                                        Nonsolvent      Methanol                                                      Washing         2 × 1L methanol, then                                                   Soxhlet extraction with                                                       methanol                                                      C(AA)B Yield    88% of theory                                                 Key Analyses    DS(butyryl) = 0.20, DS                                                        (acetoacetyl) = 0.24, IV =                                                    1.09, GPC M.sub.n = 31,000, Tg >                                              225, soluble in water,                                                        DMSO and NMP.                                                 ______________________________________                                    

This example demonstrates synthesis of a water-soluble celluloseacetoacetate butyrate by this process. C(AA)B is cellulose acetoacetatebutyrate.

EXAMPLE 4

Reagents set forth below were subjected to the standard proceduredescribed above under the standard reaction conditions, except asdescribed below. The results, in terms of identity and yield of thedesired cellulose acetoacetate ester, and key analyses of the product,are also set forth below.

    ______________________________________                                        Cellulose       Microcrystalline cellulose                                    Carboxylic Anhydride                                                                          Butyric Anhydride                                             Equiv           1.5                                                           Addition Time A 17 min                                                        Hold Time A     23 min                                                        Equiv Diketene  1.5                                                           Addition Time D 17 min                                                        Hold Time D     30 min                                                        Nonsolvent      Methanol                                                      Washing         1 × 1L water, then 1 × 1L                                         methanol, then reprecipi-                                                     tation of the solid prod-                                                     uct from acetone solution                                                     into water (washed with 2 ×                                             1L water)                                                     C(AA)B Yield    79% of theory                                                 Key Analyses    DS(butyryl) = 1.33, DS                                                        (acetoacetyl) = 1.37, IV =                                                    1.11, GPC Mn = 47,000, Tg =                                                   136, soluble in DMSO,                                                         2-butanone, acetic acid,                                                      acetone, tetrahydrofuran,                                                     chloroform, dichloro-                                                         methane and NMP.                                              ______________________________________                                    

This demonstrates the ability of the process to prepare a high-DS C(AA)Ewhich is soluble in a broad range of organic solvents, with goodutilization of the diketene and carboxylic anhydride. C(AA)B iscellulose acetoacetate butyrate.

EXAMPLE 5

Reagents set forth below were subjected to the standard proceduredescribed above under the standard reaction conditions, except asdescribed below. The results, in terms of identity and yield of thedesired cellulose acetoacetate ester, and key analyses of the product,are also set forth below.

    ______________________________________                                        Cellulose       Microcrystalline cellulose                                    Carboxylic Anhydride                                                                          Acetic anhydride                                              Equiv           1.5                                                           Addition Time A 32 min                                                        Hold Time A     30 min                                                        Equiv Diketene  0.3                                                           Addition Time D 12 min                                                        Hold Time D     37 min                                                        Nonsolvent      Methanol                                                      Washing         2 × 1L methanol then                                                    Soxhlet extraction                                                            with methanol                                                 CA(AA) Yield    76% of theory                                                 Key Analyses    DS(acetyl) = 1.37, DS                                                         (acetoacetyl) = 0.41, IV =                                                    1.08, GPC Mn = 43,000, Tg =                                                   204, soluble in DMSO and                                                      NMP.                                                          ______________________________________                                    

This example differs from the general procedure in that the diketene wasadded first, then the carboxylic anhydride. This example demonstratesthat reversal of the order of addition of diketene and carboxylicanhydride also affords a homogeneously substituted, soluble C(AA)E.Table I compares the results from this experiment, and two essentiallyidentical experiments in which the only variable is the order ofaddition. In one experiment (B) the order of addition was reversed fromthat of Example 5 (A); in another experiment, the diketene and aceticanhydride were premixed and added together. It is evident that mostanalytical properties measured are similar, but that the Tg variessignificantly with method of addition. This provides another inexpensivetool for control of product properties.

                                      TABLE I                                     __________________________________________________________________________    Cellulose Acetate Acetoacetate                                                Experiment on Properties and Substitution vs. Mode of Addition                Ac.sub.2 O DIK  Order of                                                                            DS DS DS     GPC                                                                              Tg  Solubility                          Experiment                                                                          EQUIV.                                                                             EQUIV.                                                                             Addition                                                                            Ac AA (TOT)                                                                             IV Mn (°C.)                                                                      DMSO                                                                              NMP                             __________________________________________________________________________    A     1.50 0.30 DIK, Ac.sub.2 O                                                                     1.37                                                                             0.41                                                                             1.78                                                                              1.08                                                                             42.9                                                                             204 S   S                               B     1.50 0.30 Ac.sub.2 O, DIK                                                                     1.28                                                                             0.36                                                                             1.64                                                                              0.95                                                                             41.4                                                                             190 S   S                               C     1.50 0.30 Mixed 1.37                                                                             0.43                                                                             1.80                                                                              1.01                                                                             40.1                                                                             194 S   S                               __________________________________________________________________________     DIK = Diketene                                                                Ac = Acetyl                                                                   AA = Acetoacetate                                                             Ac.sub.2 O '2 Acetic anhydride                                                All GPC Mn values have been divided by 1000                                   All runs used microcrystalline cellulose                                      S = Soluble                                                                   Mixed = Diketene and Ac2O were mixed prior to addition                   

                  TABLE II                                                        ______________________________________                                        C(AA)E Solution Viscosities                                                                    DS           Solution (1) Viscosity                          Sample  Bu       AcAc    OH   38% Solids, cP                                  ______________________________________                                        175     1.97   0.50      0.53  36,000                                         178     1.90   0.53      0.57   4,600                                         181     1.73   0.87      0.40  17,500                                         184     1.89   0.47      0.64  30,000                                         187     1.95   0.64      0.41  15,000                                         CAB     1.73   0         0.45 >700,000                                        CAB     2.12   0         0.75  665,000                                        ______________________________________                                         DS (Bu and AcAc of C(AA)Es determined by proton NMR.                          DS (OH) determined by difference.                                             CABCellulose Acetate Butyrate                                                 (1) Solution Formula (all weight percents):                                   C(AA)E 38%                                                                    Butylbenzyl Phthalate 2%                                                      Ethylene glycol propyl ether 15%                                              Ethylene glycol butyl ether 15%                                               Ethyl 3ethoxy propionate 30%                                             

                                      TABLE III                                   __________________________________________________________________________    C(AA)E Dispersion Film Properties                                                    DS     Dispersion (1)    Dispersion, Crosslinked (2)                   Sample                                                                            Bu AcAc                                                                              OH Tukon(3)                                                                           MEK Rubs                                                                            Water Rubs                                                                           Tukon                                                                              MEK Rubs                                                                            Water Rubs                         __________________________________________________________________________    106 2.37                                                                             0.45                                                                              0.18                 6.1  19    300                                110 2.53                                                                             0.26                                                                              0.21                 5.7  20    60                                 178 1.90                                                                             0.53                                                                              0.53                                                                             15.8 2     1000        50    750                                178F                                                                              1.84                                                                             0.61                                                                              0.55                                                                             6.1  10    325    16.9 880   1000                               196-33                                                                            1.76                                                                             0.62                                                                              0.62                                                                             19.0 20    1000   18.2 1000  760                                196-22                                                                            1.83                                                                             0.66                                                                              0.51                                                                             17.8 40    425    20.0 1000  400                                CAB 1.72                                                                             0.00                                                                              0.45    9000         2.8  15    58                                 __________________________________________________________________________     (1) Dispersion Formula                                                        Table II Solution 50 parts                                                    Water 50 parts                                                                Mix with high shear dispersion.                                               Add surfactant if needed.                                                     (2) Crosslinked Dispersion Formula                                            Dispersion Formula 100 parts                                                  American Cyanamid Cymel 373  (Methoxy methyl methylol melamine resin) 5       parts                                                                         Water 5 parts                                                                 Baked 30 min @ 250° F.                                                 (3) Tukon method  Tukon hardness  ASTM Method D1474 knoops hardness numbe      ASTM Method D3363                                                            (4) MEK rubs  ASTM D1308  methylethyl ketone (MEK) dynamic rub test           (5) Water Rubs  ASTM Method D1308                                             (6) CAB  Cellulose Acetate Butyrate                                      

                                      TABLE IV                                    __________________________________________________________________________    C(AA)E Solution Film Properties                                                            Solution (1)                                                                           Enamine Formating (2)                                                                       Michael Reation (3)                                                                            Isocyanate (4)           Sam-              Water         Water                                         ple                                                                              Bu AcAc                                                                              OH Tukon(5)                                                                           Rubs                                                                              Tukon                                                                             MEK Rubs                                                                            Rubs                                                                              Tukon                                                                             MEK Rubs                                                                            Water Rubs                                                                           Tukon                                                                             MEK                  __________________________________________________________________________                                                             Rubs                 101                                                                              2.37                                                                             0.45                                                                              0.18                                                                             18.7 50  2.9 25    1000                                                                              10.5                                                                              10    135    16.2                                                                              127                  110                                                                              2.53                                                                             0.26                                                                              0.21                                                                             10.3 38                                 13.0                                                                              162                  118                                                                              2.97                                                                             0.02                                                                              0.01                                                                             6.8  25  10.0                                                                              25    275 10.6                                                                              10    970    13.5                                                                              8                    131                                                                              2.68                                                                             0.20                                                                              0.12                                                                             11.2 19                                                          CAB                                                                              2.12                                                                             0.00                                                                              0.75                                                                             19.0     5.2 10    1000                                                                              11.6                                                                              40    285    16.4                                                                              104                  CAB                                                                              1.72                                                                             0.00                                                                              0.45                                                                             18.0 20                                 16.0                                                                              200                  __________________________________________________________________________     (1) Solution Formula                                                          Cellulose Ester 30%                                                           nButyl Acetate 30%                                                            2Heptanone 30%                                                                Ektapro EEP 10%                                                               (2) Enamine Formulation                                                       Solution Formula 100 parts                                                    Jeffamine D400 2 parts                                                        Bake 30 min at 250° F.                                                 (3) Michael Reaction                                                          Solution Formula 100 parts                                                    PMPTA 2 parts                                                                 5% DBU 0.8 parts                                                              Bake 30 min at 25° F.                                                  (4) Isocyanate Reaction                                                       Solution Formula 100 parts                                                    Miles Desmodur N75 11 parts                                                   10% Dibutyltin dilaurate 0.25 parts                                           Air dry 24 hours. Age 48 hours at 120° F.                              (5) Tukon  Tukon hardness, Knoops hardness number                             TMPTA  Trimethylolpropane triacrylate                                         DBU  1,8diazabicyclo[5.4.0]undec7-ene                                         CAB  Cellulose Acetate Butyrate                                               EEP  Ethyl3-ethoxy propionate                                                 Jeffamine D400  a polyamine commercially available from Texaco, Inc.          Tukon method  Tukon hardness  ASTM Method D1474 Knoops hardness number        ASTM Method D3363                                                             MEK rubs  ASTM Method D1308  methylethyl ketone (MEK) dynamic rub test        Water rubs  ASTM Method D1308                                            

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention. Moreover, all patents, patent applications (published orunpublished, foreign or domestic), literature references or otherpublications noted above are incorporated herein by reference for anydisclosure pertinent to the practice of this invention.

We claim:
 1. A coating composition comprising:(A) about 20 to about 80percent, based on the weight of the total coating composition, of acellulose acetoacetate ester having a DS/AGU of 0.1 to 2.9, (B) about 20to about 80 percent, based on the weight of the total coatingcomposition, of a coating solvent.
 2. The coating composition of claim 1wherein component (A) is present at 30 to 50 percent, and component (B)is present at 50 to 70 percent, based on the weight of the total coatingcomposition.
 3. The coating composition of claim 1 wherein said coatingsolvent is selected from the group consisting of glycol ethers, ketones,and esters.
 4. The coating composition of claim 3 wherein said coatingsolvent is selected from the group consisting of ethylene glycol butylether, ethylene glycol propyl ether, methyl amyl ketone, n-heptanone,n-butyl acetate, ethyl-acetate, and ethylene glycol ether.
 5. A coatingcomposition comprising:(A) about 25 to about 75 percent, based on theweight of the total coating composition, of the cellulose acetoacetateester product of claim 1, (B) about 25 to about 75 percent, based on theweight of the total coating composition, of water.
 6. The coatingcomposition of claim 5 wherein component (A) is present at 50 percentand component (B) is present at 50 percent based on the weight of thetotal coating composition.
 7. A coating composition comprising:(A) about80 to about 95 percent, based on the weight of the total coatingcomposition, of the cellulose acetoacetate ester product of claim 5, (B)about 1 to about 15 percent, based on the weight of the total coatingcomposition, of a crosslinking agent, and (C) 0 to about 19 percent,based on the weight of the total coating composition, of water.
 8. Thecoating composition of claim 7, wherein component (A) is present at 85to 90 percent, component (B) is present at 4 to 10 percent, andcomponent (C) is present at 0 to 10 percent, based on the weight of thetotal coating composition.
 9. The coating composition of claim 7 whereinsaid crosslinking agent is a melamine resin, a urea resin, anamine-containing resin or a mixture thereof.
 10. The coating compositionof claim 9 wherein said crosslinking agent is hexamethoxymethylmelamine,hexabutoxymethylmelamine, tetramethoxymethylurea,tetrapropoxymethylurea, an amine terminated polyamide, an amineterminated polyoxyethylene, an amine terminated polyoxypropylene, or amixture thereof.
 11. A coating composition comprising:(A) about 85 toabout 99 percent, based on the weight of the total coating composition,of the cellulose acetoacetate ester product of claim 1, (B) about 1 toabout 15 percent, based on the weight of the total coating composition,of a crosslinking agent, and (C) about 0 to about 2% percent, based onthe weight of the total coating composition, of a catalyst.
 12. Thecoating composition of claim 11 whereincomponent (A) is present at 87 to95 percent, component (B) is present at 2 to 12 percent, and component(C) is present at 1 to 10 percent.
 13. The coating composition of claim11 wherein said crosslinking agent is an isocyanate-containing resin.14. The coating composition of claim 13 wherein saidisocyanate-containing resins is selected from the group consisting ofresins based on hexamethoxydiisocyanate, toluene diisocyanate, and MDI.15. The coating composition of claim 1 wherein said cross-linking agentis trimethylolpropane triacrylate and said catalyst is1,8-diazabicyclo[5.4.0]-undec-7-ene.
 16. The coating composition ofclaim 14 wherein said isocyanate-containing resin is Desmodur N-75 andsaid catalyst is dibutyltindilaurate.
 17. The coating composition ofclaims 1, 5, 7 or 11 additionally containing up to about 70 percent,based on the weight of the cellulose acetoacetate ester, of at least oneadditional coating additive.